hdu 1208 pascal travel

好簡單的一個題目，放在搜尋專題裡，大家都以為難，老師跑過來說這道題很簡單，叫我做一下。。

有點變態的就是直接一個一個資料讀進去沒運行結果出，改成字串讀進去就可以。有點搞不懂。

Pascal's Travels Time Limit : 2000/1000ms (Java/Other)   Memory Limit : 65536/32768K (Java/Other)Total Submission(s) : 6   Accepted Submission(s) : 4Font: {
ProFont('Times New Roman')
}">Times New Roman | {
ProFont('Verdana')
}">Verdana | {
ProFont('Georgia')
}">Georgia Font Size: {
ProFontAdd(-1)
}">← {
ProFontAdd(1)
}">→{
ObjFolder('procon')
}">Problem DescriptionAn n x n game board is populated with integers, one nonnegative integer per square. The goal is to travel along any legitimate path from the upper left corner to the lower right corner of the board. The integer in any one square dictates how large a step away from that location must be. If the step size would advance travel off the game board, then a step in that particular direction is forbidden. All steps must be either to the right or toward the bottom. Note that a 0 is a dead end which prevents any further progress.

Consider the 4 x 4 board shown in Figure 1, where the solid circle identifies the start position and the dashed circle identifies the target. Figure 2 shows the three paths from the start to the target, with the irrelevant numbers in each removed.

Figure 1

Figure 2{
ObjFolder('proinput')
}">InputThe input contains data for one to thirty boards, followed by a final line containing only the integer -1. The data for a board starts with a line containing a single positive integer n, 4 <= n <= 34, which is the number of rows in this board. This is followed by n rows of data. Each row contains n single digits, 0-9, with no spaces between them.{
ObjFolder('prooutput')
}">OutputThe output consists of one line for each board, containing a single integer, which is the number of paths from the upper left corner to the lower right corner. There will be fewer than 2^63 paths for any board. {
ObjFolder('prosamplein')
}">Sample Input

423311213123131104333212131232212051110101111111111110111101-1

{
ObjFolder('prosampleout')
}">Sample Output

307

#include<iostream>
using namespace std;
#define max 50
int a[max][max];
__int64 sum[max][max];
int main()
{
    int n,i,j;
    char ch[50];
    while(scanf("%d",&n)!=EOF)
    {
       getchar();
       if (n==-1) return 0;
       for(i=0;i<n;i++)
       {
         gets(ch);
         for(j=0;j<n;j++)
         a[i][j]=ch[j]-'0';
       }
       memset(sum,0,sizeof(sum));
       sum[0][0]=1;
       for (i=0;i<n;i++)
       {
         for (j=0;j<n;j++)
        {
            if (a[i][j]==0) continue;
            sum[i+a[i][j]][j]+=sum[i][j];
            sum[i][j+a[i][j]]+=sum[i][j];
        }
       }
       cout<<sum[n-1][n-1]<<endl;
    }
    return 0;
}